In a known manner, large works, such as catalogues, dictionaries, year books, encyclopedias, etc., which are intended to be handled very frequently are bound either permanently, using flexible materials such as paper, fabric, leather or plastics, or such that the pages may be removed, using spiral bindings or files, leading to rapid wear of the pages and/or of the binding of the work.
It has already been proposed, for example in document GB-A-0,597,192, to produce a book, particularly a book for children, in which the printed portion of the sheets is contained in a surface ending a certain distance from one of the edges of the sheet, so as to leave a relatively wide intact margin adjacent to this edge. This margin is perforated with two or more circular holes, extending through the covers and all the sheets of the book and spaced from this edge to receive the fasteners of a file. The sheets of the book are joined together by a thread or by any other fastening means arranged opposite the circular perforations in order to consolidate and reinforce the edge of the book at points opposite the circular perforations.
Also known, from document U.S. Pat. No. 2,706,645, is a book including a body of sheets, flyleaves, a board reinforcement on each side of the sheets which are joined to board cover sheets. Fastenings extend through the body of the sheets, the flyleaves and the board reinforcements. A protective sheath is glued to the outer portion of the board cover sheets, of the join and of the board reinforcements. It extends around the spine of the book and covers over the fastenings. The flyleaves are glued to the inner surface of the board cover sheets and of the joins.
Also known, from document FR-A-2,464,827, is a process for assembling sheets, according to which a flyleaf is placed on top of and underneath a stack of sheets, the stack of sheets is pierced along one of the edges of the stack, spikes formed on a strip of heat-sealable material are inserted into the holes, another band of heat-sealable material, pierced with corresponding holes, is arranged over the spikes, the two strips are pressed together, the second strip is welded over the spikes of the first strip, and a strong cardboard sheet is glued on each flyleaf. The cardboard sheet is of a size which is slightly smaller than that of the surface of the flyleaf left free by the heat-sealable strip so that it can be glued at a sufficient distance from this strip and thus be allowed to pivot freely about its border which faces the heat-sealable strip.
These known processes and devices are unsuitable for printed works containing a large number of pages and, above all, they do not make it possible to protect the sheets of the bound work when the latter is consulted frequently.